Multifocal choroiditis with overlying retinal detachment occurs after carotid injection of certain bacteria in dogs. The ocular lesions occur mainly in the tapetal area of the retina, correlate with microabscesses in the inner choroid and subretinal space, and occasionally occur in the inner retina and anterior uveal tract. The major pathophysiologic factor involved in the dog model of septic choroiditis appears to be embolization of the choriocapillaries by "live" bacteria which clump and adhere well to tissues. In the dosages used, antibiotics did not prevent or alter the severity of the fundus lesions. In pigtail monkeys carotid injection of a dextran producing strain of Streptococcus mutans consistently caused fundus lesions clinically resembling those seen in humans with bacteremia. In contrast to the dog model the lesions in the monkey occurred mainly in the retina but also in the choroid and optic nerve.